Demands on robots for household purposes as well as industrial purposes, are increasing, and studies on the robots are actively in progress accordingly. Particularly, unlike conventional robots held in the stationary position, studies on a movable mobile robot are actively in progress. Studies are in progress on a technique of correctly estimating its own location of the movable mobile robot using a surrounding environment and a mapping technique of allowing the movable mobile robot to grasp its own location using a reference landmark as a starting point to correctly estimate its own location of the movable mobile robot.
Particularly, information containing a specific shape such as a vertex or a straight line among information acquired from the surrounding environment is named as a feature, and a map created using the feature is referred to as a feature map. Since the feature is used as a landmark for localizing a robot in an environment, information such as which of features will be extracted and used, whether or not the extracted feature has a robust characteristic according to a change in the surrounding environment and the like becomes an important factor in creating an accurate feature map.
In general, a low-priced small robot employs an infrared sensor or a ultrasonic sensor as a sensor for detecting a state for navigation. The infrared sensor makes it difficult to achieve more accurate mapping due to information leakage caused by linearity and severe noises. In addition, the ultrasonic sensor has an advantage of having a wide sensing range, but still entails a problem in that it is difficult to achieve more accurate mapping due to severe noises.
A ceiling image-based robot including a ceiling-oriented single camera which can utilize a ceiling image has been developed in order to overcome these problems. Such a ceiling-oriented single camera-equipped robot has an advantage in that it may exclude an interference caused by a dynamic object such as a person or an obstacle and stably trace a landmark. However, the conventional ceiling-oriented single camera-equipped robot according to the prior art uses a corner feature and a straight line feature as features. The corner feature may be stably matched, but has a drawback in that information is severely changed by a change in brightness according to the change of illumination or the like. In addition, the straight line feature has a shortcoming in that it makes it difficult to determine whether or not the straight line feature is correctly matched due to confusion when a plurality of straight line features is provided.
In Korean Patent Registration No. 10-0871115, various studies are conducted on localization of a mobile robot, such as selecting a method for reducing a load and increasing accuracy through a technique of extracting and removing unnecessary feature points among image data for recognizing a ceiling image.
In addition, in case of the ceiling image, rapid localization is difficult due to a computation load of image features, and there is a difficulty in that rapid localization should be enabled and simultaneously robustness of the features of the ceiling should be secured to perform an accurate localization.
In addition, since a conventional method of recognizing an image of a ceiling is performed in a simplest and formalized environment, i.e., focusing on formalized features such as an illumination feature, a straight line feature and a corner feature, it is quite difficult to secure generality in a new environment.